1. Field of the Invention
The present invention generally relates to automatic determination of the pitch and the yaw of a launched projectile from recorded launch video taken of the projectile in flight.
2. Description of the Related Art
Live-fire testing of artillery projectiles is commonly conducted for design changes or lot-acceptance verification. In these tests, it is becoming increasingly common to record high-speed video of the projectiles as they exit the muzzle of the cannon. Often, these cameras are stationary digital cameras capable of recording up to 100,000 frames per second (fps). In some instances, when visual confirmation of the initial flight performance is desired, new state-of-the-art camera systems capable of automated rotating to follow a projectile are used.
Some of these camera systems utilize an optical system that works by rotating a mirror at a calculated rate, so that the projectile remains in the camera field of view for more than 100 m (meters) following muzzle exit. For example, a successful “track” of a 155 mm (millimeter)-type artillery projectile can deliver thousands of high-resolution digital images of the projectile during the first few moments of free-flight. Depending on the zoom and position of the camera, the resolution quality of these images can deliver hundreds of pixels along the length of the projectile. Analysis of this large amount of data can be difficult and time consuming, when trying to determine the position and motion of the projectile.
Manual analysis requires manual data reduction of stationary video system launch video in which an operator plays a launch video and identifies relative angles between the background and regions of the bullet to estimate position. Limitations of this type of analysis are that it is labor-intensive, limited to the precision of the image resolution, and it is subject to human error. In addition, a stationary field of view makes it difficult to measure the observed pitch angle in more than one location along the line of fire. Typically, pitch and yaw high speed cameras are pointed at an estimated location of the first-maximum yaw (FMY). This type of analysis requires precise knowledge of both the location and orientation of all cameras used.
More recent prior art methods utilize computer analysis of projectiles by tracking specific features on objects in artillery launch video. Results from different cameras can be combined to quantify 6 degrees-of-freedom (DOF) motion. Some limitations of this type of analysis are that it requires the operator to be trained in the specific program, and often requires user interaction to re-select tracked points several times during the video. These systems may not be practical if analyzing hundreds of video frames worth of data.